Official campaigning began Tuesday for key Lower House by-elections in Osaka and Okinawa prefectures in what is seen as a prelude to the Upper House election this summer.
Prime Minister Shinzo Abe's ruling Liberal Democratic Party is competing with opposition candidates seeking to streamline administrations in Osaka and block a controversial government plan to relocate a U.S. military base within Okinawa.
The April 21 by-elections coincide with the second batch of local elections to be held simultaneously across the country. In the first round on Sunday, the LDP garnered broad voter support by winning a key gubernatorial race in Hokkaido and a majority of prefectural assembly seats, but party divisions were revealed in some regional areas.